The Scientific Core is responsible for handling the overall aspects of tissue preparation and distribution once monkeys have completed the behavioral studies as well as conducting the final MRI scans on all subjects and preparing and archiving DNA samples. The specific aims of this core are as following: 1) To conduct and then analyze MRI scans on all monkeys before perfusion to enable quantitative volumetric analyses of the brain. 2) To conduct all perfusions of monkeys both in Boston and if necessary at the Yerkes Regional Primate Research Center. 3) To prepare and distribute optimally prepared fresh or frozen tissue samples to each of the Projects. 4) To construct a DNA library of normal young adult monkeys and prepare, conduct differential display analyses of RNA expression in each monkey and archive and store DNA samples from all of the monkeys. 5) To cut serial whole hemisphere sections from one hemisphere of each of the subjects. All sections will be divided into series and saved. The core will distribute series of cryostat or freezing microtome sections as need to the Projects and will itself prepare four archival series of stained sections (thick and thin thionin series, a myelin series and a H&E series) for analysis by all of the projects. 6) To arrange for postmortem necropsies on all subjects and send the results to the Animal Records Review Committee of the Animal Core which will ensure that there are no occult diseases that could confound our observations on the relationship of age-related changes in the brain to changes in cognitive function. & To encourage and make available to other investigators both brain tissue and other tissues form our monkeys to those interested in studies of aging, so long as those tissues are not needed for the specific aims of this Program. In this regard, we will also provide access to the monkey DNA library prepared by the core.